This application claims the priority of German Patent Application Serial No. 101 12 738.3, filed Mar. 16, 2001, the subject matter of which is incorporated herein by reference.
The present invention relates, in general, to a dashboard for a motor vehicle, and in particular to a dashboard support placed transversely between windshield pillars of the vehicle body.
A dashboard support includes typically a support beam, e.g. a tube which is placed between the windshield pillars. An example of a dashboard support, involved here, is disclosed in German Pat. No. DE 196 20 919 A1. Disclosed in German Pat. No. DE 195 34 568 A1 is a dashboard support in the form of a rigid support beam. In the area of the cockpit, various mountings are provided on the dashboard for retaining the instrument panel as well as further vehicle components, such as vehicle heating, ventilating and air conditioning system, airbag, steering column, center console, fuse box or glove compartment. The dashboard support is intended to satisfy several functions. Apart from reinforcing the vehicle body, the dashboard support should be able to absorb energy in the event of a collision, to connect various spatial points and allow attachment of various mountings. In addition, the dashboard support should be suitable for operation in different frequency ranges.
To date, the cross section as well as the wall thickness of dashboard supports are sized according to the first resonant frequency. Still, the dashboard support oscillates during operation of the vehicle so that vibrations and/or structure-borne sound is generated, adversely affecting the acoustics inside the motor vehicle as well as the running behavior and riding comfort for the passengers. Attempts were made to fixate or to constructively optimize the resonant frequencies, by providing a mounting on the dashboard support for attachment of the dashboard support to the vehicle body.
European Pat. No. EP 0 585 875 B1 or German Pat. No. DE 693 28 148 T2 describe a vibration damping system for a motor vehicle, including a vibration sensor for detecting and evaluating vibration of the motor vehicle or parts thereof and vibration of air inside the vehicle. In response to vibration, two vibrators are excited in such a manner that the vehicle vibration and the air vibration are damped inside the vehicle.
It would be desirable and advantageous to provide an improved dashboard support to enhance the design freedom as far as cross section and wall thickness are concerned while reducing the overall weight.
According to one aspect of the present invention, a dashboard support for a motor vehicle, includes a support beam extending between windshield pillars of a motor vehicle body; and an active arrangement, interacting with the support beam, for implementing a vibration damping.
The present invention resolves prior art problems by associating an active arrangement for vibration damping to the support beam. When the dashboard support vibrates during operation of the vehicle, the vibration is detected by a sensor and damped by an actively produced compensating vibration and thereby effectively negated or shifted to another, especially higher, frequency range. The arrangement intervenes actively and induces periodic deformation amplitudes and voltage amplitudes to effectively obliterate the vibration or dampen the frequency in suitable phase position. Moreover, the arrangement is able to decouple interconnected components so as to further promote a vibration damping. A transmission of vibrations and of a force flux in connection areas of adjoining components is hereby avoided.
The effectiveness of the dashboard support and in particular of the active arrangement is thus based on vibration damping, a shift to other frequency ranges and/or decoupling of interconnected components. As a result, the cross section of a dashboard support according to the present invention can thus be simplified and made smaller. Also a reduction in wall thickness is possible, leading to a weight decrease. The riding comfort is enhanced and the need for separate mountings for attachment can be omitted so that the overall construction becomes simpler and the weight can be further reduced. Thus, a dashboard support according to the present invention enables an active suppression of vibrations and noise so that the running behavior as well as the riding comfort is improved.
There are various physical systems possible to provide an active vibration damping, only several of which will be detailed here. Suitable systems include components which have electrically or magnetically activateable materials as actuators and/or sensors and are operatively connected to a controller. Operation of actuator/sensor elements may be based on piezoelectric technology, magnetoresistance technology or also electro-rheological fluids.
Of course, an arrangement for active vibration damping in accordance with the present invention may also be used for retrofitting exiting dashboard supports.
According to another feature of the present invention, the active arrangement for vibration damping may include adaptive piezoelectric elements, which are arranged on the support beam, and an active controller, which is operatively connected to the piezoelectric elements. Piezoelectric elements involved here may include piezo-ceramic actuator/sensor elements which may be configured as fiber composite having embedded therein piezo-ceramic fibers and/or foils. Especially suitable is the use of thin piezo-ceramic plates, also called piezo foils, as well as piezoelectric ceramic fibers for integration in fiber composites.
Basically, it is possible to provide piezoelectric elements also on the steering column or adjoining mountings of the dashboard support.
Adaptive piezoelectric elements convert electric energy into mechanical energy without assistance of moving parts. Thus, the arrangement reacts very rapidly while still exhibiting a long service life. The piezoelectric effect is based on a mechanical deformity of certain embedded crystals under the influence of an electric field. This effect is used to realize an active excitation of the piezoelectric elements via the external controller and the generation of a counter or compensating vibration. In other words, a vibration is imparted at a frequency in near agreement with the resonant frequency of the dashboard support in a direction to compensate the vibration of the dashboard support. Examples of piezo-electric ceramic actuators include ceramic mixtures of lead, zirconate and titanate with high electromechanical activity, i.e. great relative length/thickness change when electric voltage is applied.
Piezoelectric elements may also be distributed along the dashboard support. In this way, it is possible to employ the piezoelectric elements for damage recognition. For example, when the dashboard support has cracks or is damaged as a result of breaks, the piezoelectric elements are able to sense these cracks or breaks as a result of a change in the vibration behavior.
Piezoelectric elements may be positioned in the attachment zone between the windshield pillars and the support beam. Also the attachment zone of the steering column allows the disposition of the piezoelectric elements because a major part of oscillations or vibrations caused during operation are channeled via the steering column to the dashboard support. In addition, there is the possibility to dispose the piezoelectric elements on mountings arranged on the dashboard support. The disposition of piezoelectric elements between components then realizes the intended effect of decoupling to thereby interrupt the force flux.